I discovered recently a small (10-15mm in diameter), smooth, oval, lump on the right upper side of my head. The lump sticks out by about 2-4mm. There is a little bit of redness around the lump, but I am not sure if it s from me touching it or from the underlying condition. The lump is completely immobile, I can move the scalp over it, but it does not move. It feels like it s attached to the skull. It s a little painful, like a pimple, but again I am very concerned because it feel like it s attached to my skull, NOT the skin. What could it be?